Devices and Methods for Loading a Prosthesis onto a Delivery System

ABSTRACT

In an embodiment, a device for loading a prosthesis onto a delivery system comprises a cap and a reducing member. The cap has a piston member that seats a prosthesis. The piston member has at least one side wall configured to contact a portion of the side of the prosthesis seated therein. The reducing member has a conical wall, a first open end, and a second open end. The first open end is configured to receive the piston member. The reducing member reduces an external dimension of at least a portion of the prosthesis seated in the piston member as the prosthesis is moved along an inner surface of the conical wall.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to devices and methods for loading aprosthesis onto a delivery system and, particularly, to devices andmethods for loading a valve prosthesis onto a minimally invasivedelivery system, for example, a delivery catheter.

2. Background

The replacement of a deficient cardiac valve is often performed byopening a patient's thorax, placing the patient under extracorporealcirculation or peripheral aorto-venous heart assistance, temporarilystopping the heart, surgically opening the heart, excising the deficientvalve, and then implanting a prosthetic valve in its place. Thisprocedure has the disadvantage of requiring prolonged patienthospitalization, as well as extensive and often painful recovery. Italso presents advanced complexities and significant costs.

To address the risks associated with open-heart implantation, minimallyinvasive approaches have been developed to facilitate catheter-basedimplantation of valve prostheses in the heart, including a beatingheart. For example, a valve prosthesis formed by attaching a valve to aframe made of a wire or a network of wires has been proposed. Such avalve prosthesis can be contracted radially to introduce the valveprosthesis into the body of the patient percutaneously through acatheter.

To prepare such a valve prosthesis for implantation, the valveprosthesis can be initially provided in an expanded or uncrimpedcondition, then crimped or compressed around the distal tip of thecatheter assembly until the valve prosthesis is as close to or smallerthan the diameter of the distal tip as possible. Various methods anddevices are available for crimping the valve prosthesis onto thecatheter's distal tip, which may include hand-held devices or tabletopdevices, for example.

Loading a valve prosthesis on the delivery system, however, can bedifficult as the valve prosthesis and crimping device must be carefullyinserted over the distal tip of the catheter assembly without damagingthe valve or frame, including, for example, support arms of the valveprosthesis. Accordingly, a need exists for a device and method ofloading prosthesis onto a delivery system, such as a delivery catheter,that reduces the risk of damage to the prosthesis during loading.

BRIEF SUMMARY OF THE INVENTION

The present invention relates generally to devices and methods forloading a prosthesis, for example, a valve prosthesis, onto a deliverysystem such as a delivery catheter for a minimally invasive implantationof the prosthesis. Although preferred embodiments of the loading deviceare used with self-expanding prostheses, the present invention can beused with balloon-expandable or other mechanically-expanded prostheses.Preferred embodiments of the present invention permit the reduction ofan external dimension of a compressible prosthesis without damaging theprosthesis.

In an embodiment, a device for loading a prosthesis onto a deliverysystem comprises a cap and a reducing member. The cap has a pistonmember. The piston member includes a first surface that is configured tocontact one end of a prosthesis seated therein. The piston member alsoincludes at least one side wall extending from the periphery of thefirst surface. The side wall is configured to contact a portion of theside of the prosthesis seated therein. The reducing member has a conicalwall, a first open end, and a second open end. The first open end isconfigured to receive the piston member. The reducing member reduces anexternal dimension of at least a portion of the prosthesis seated in thepiston member as the prosthesis is moved along an inner surface of theconical wall. In another embodiment, the reducing member also includes acylindrical wall that defines the first open end, and wherein theconical surface defines the second open end.

In an embodiment, a method for loading a prosthesis onto a deliverysystem comprises passing a distal end of a delivery system through afirst open end and a second open end of a reducing member; seating theprosthesis in a piston member of a cap, which contacts a portion of aside of the valve prosthesis with at least one side wall extending fromthe piston member; inserting the distal end of the delivery system intothe center of the valve prosthesis and an opening defined by the pistonmember; and advancing the valve prosthesis retained in the piston memberalong an inner surface of a conical wall of the reducing member towardsthe first open end of the reducing member. In another embodiment, themethod includes coupling the other end of the valve prosthesis to avalve retainer of the delivery system, and advancing a valve retainersleeve over portions of the valve prosthesis that have been advancedalong the conical wall of the reducing member.

Additional features of the invention will be set forth in thedescription that follows. Both the foregoing general description and thefollowing detailed description are exemplary and explanatory and areintended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE FIGURES

The accompanying figures, which are incorporated herein, form part ofthe specification and illustrate exemplary embodiments of the presentinvention. Together with the description, the figures further serve toexplain the principles of and to enable a person skilled in the relevantart(s) to make and use the exemplary embodiments described herein. Inthe drawings like reference characters indicate identical orfunctionally similar elements.

FIG. 1 illustrates an exemplary delivery system used with loadingdevices according to embodiments of the present invention.

FIG. 2 illustrates an exemplary prosthesis that can be loaded onto adelivery system using loading devices according to embodiments of thepresent invention.

FIG. 3 illustrates a loading device having a cap and a reducing memberaccording to an embodiment of the present invention.

FIG. 4A illustrates a cross section of the reducing member of FIG. 3through the center of the reducing member.

FIG. 4B illustrates the reducing member of FIGS. 3-4A from the distalend of the reducing member.

FIG. 5 illustrates an alternate embodiment of a cap according to thepresent invention.

FIG. 6A illustrates the cap of FIG. 5 from the proximal end of the cap.

FIG. 6B illustrates a cross section of the cap of FIGS. 5-6A through thecenter of the cap.

FIG. 7 illustrates an alternate embodiment of a cap having an optionalfriction interface.

FIG. 8 illustrates the loading device at a stage of the loading processat which the distal tip assembly is inserted through the reducingmember.

FIG. 9 illustrates the loading device at another stage of the loadingprocess at which the valve prosthesis is seated in the cap.

FIG. 10 illustrates the loading device at another stage of the loadingprocess at which the cap and the valve prosthesis are inserted over thedistal tip assembly.

FIG. 11 illustrates the loading device at another stage of the loadingprocess at which the cap is advanced towards the reducing member tocrimp the valve prosthesis.

FIG. 12 illustrates the loading device at another stage of the loadingprocess at which the reducing member is aligned with the valve retainer.

FIG. 13 illustrates the loading device at another stage of the loadingprocess at which the valve prosthesis is coupled with the valveretainer.

FIG. 14 illustrates the loading device at another stage of the loadingprocess at which the valve retaining sleeve is advanced over the crimpedportion of the valve prosthesis.

FIG. 15 illustrates the loading device at another stage of the loadingprocess at which the valve prosthesis is loaded on the delivery system.

FIG. 16 illustrates the loading device at another stage of the loadingprocess at which the cap is removed from the loaded valve prosthesis andreducing member.

DETAILED DESCRIPTION OF THE INVENTION

The following detailed description of the present invention refers tothe accompanying figures that illustrate exemplary embodiments. Otherembodiments are possible and may fall within the scope of the presentinvention. Modifications can be made to the exemplary embodimentsdescribed herein without departing from the spirit and scope of thepresent invention. Therefore, the following detailed description is notmeant to be limiting. The operation and behavior of the exemplaryembodiments presented are described with the understanding that variousmodifications and variations of the exemplary embodiments may be withinthe scope of the present invention.

FIG. 1 illustrates an exemplary embodiment of a catheter assembly 100.Catheter assembly 100 is described and illustrated herein to facilitatedescription of the loading devices according to embodiments of thepresent invention. Any number of alternate delivery systems, includingother delivery catheters, can be used with the loading devices describedherein. Catheter assembly 100 is merely exemplary.

Catheter assembly 100 has a proximal end 102 and a distal end 104.Catheter assembly 100 generally includes a handle assembly 106 locatedat proximal end 102, a distal tip assembly 108 located at distal end104, and an outer delivery shaft 110 between distal tip assembly 108 andhandle assembly 106. Outer delivery shaft 110 can retain a degree offlexibility. Distal tip assembly 108 includes a tip 112. Catheterassembly 100 can be advanced along a guide wire (not shown).

Catheter assembly 100 further includes a valve retaining sleeve 114 anda valve retainer 116. Valve retaining sleeve 114 is coupled to thedistal end of the outer delivery shaft 110. Valve retainer 116 iscoupled to an intermediate delivery shaft 118. Valve retainer 116 caninclude a plurality of slots 120 at the distal end of valve retainer 116as shown in FIG. 13. Outer delivery shaft 110 extends from the interiorof handle assembly 106 to valve retaining sleeve 114. Tip 112 is coupledto the distal end of intermediate delivery shaft 118. Intermediatedelivery shaft 118 extends from the interior of handle assembly 106 totip 112, to which the distal end of intermediate delivery shaft 118 iscoupled. Intermediate delivery shaft 118 is encompassed by outerdelivery shaft 110 from the interior of handle assembly 106 until theouter delivery shaft 110 ends at valve retaining sleeve 114.Intermediate delivery shaft 118 is preferably a tubular member.

FIG. 2 illustrates an exemplary valve prosthesis 200. Valve prosthesis200 is described and illustrated herein to facilitate description of theloading devices according to embodiments of the present invention. Anynumber of alternate prostheses can be used with the loading devicesdescribed herein. Valve prosthesis 200 is merely exemplary.

Valve prosthesis 200 includes support frame 202, valve leaflets 204located towards the distal end 206 of valve prosthesis 200, and valveskirt 208. Support frame 202 includes coupling members 210 dependingfrom a proximal end 212 of valve prosthesis 200. Support frame 202 ispreferably formed of a self-expanding material, for example, nitinol.Other self-expanding or shape memory materials can be used instead ofnitinol.

Preferably, three valve leaflets 204 are provided to form a tricuspidvalve structure within valve prosthesis 200. Alternate valve leafletconfigurations, for example, bicuspid valves, can be included in valveprostheses used with the loading devices and methods described herein.Valve leaflets 204 and skirt 208 can be formed from animal pericardiumtissue, for example, bovine pericardium or porcine pericardium. In otherembodiments, leaflets 204 and skirt 208 can be formed from syntheticmaterials. Leaflets 204 and skirt 208 are attached to support frame 202,preferably using sutures, as shown in FIG. 2. Alternately, various typesof sutureless bonding methods can be used to attach leaflets 204 andskirt 208 to frame 202.

Coupling members 210 extend from proximal end 212 of support frame 202and include eyelets or tabs at their proximal end. Coupling members 210,which are optional, can be formed in various configurations other thanthat shown. For example, coupling members 210 can be J-shaped hooks, orcoupling members 210 can take on any number of sizes or shapes whileremaining compatible with the loading devices and methods describedherein.

Support frame 202 further includes three support arms 214 that can beattached to support frame 202 towards its distal end. Alternately,support arms 214 can be formed integrally with support frame 202.Support arms 214 are preferably formed of a self-expanding material, forexample, nitinol. Other self-expanding or shape memory materials can beused instead of nitinol. Support arms 214 can be attached to supportframe 202 such that they are biased away from support frame 202 but canpivot radially with respect to support frame 202. Support frame 202 canfurther include a plurality of barbs 216 towards the proximal end ofsupport frame 202. Barbs 216 extend for a distance towards the distalend of support frame 202. Preferably, barbs 216 extend in anapproximately axial direction. Barbs 216, which are optional, can alsobe biased or curved slightly inward, but with less inward curve than thesurrounding section of support frame 202. Because the distal end ofbarbs 216 define a greater diameter than the surrounded support frame,barbs 216 receive the majority of forces when the proximal end ofsupport frame 202 is loaded using the techniques described herein. Thisprevents damage to support frame 202 and, more particularly, to thesutures that attach skirt 208 to support frame 202.

FIGS. 3, 4A, and 4B illustrate a loading device 300 for loading aprosthesis frame onto a delivery system according to an embodiment ofthe present invention. Loading device 300 includes a cap 302 and areducing member 304. Cap 302 has a distal end 306, a proximal end 308,and a longitudinal axis A. Cap 302 includes a circular base 310 atdistal end 306. A cylindrical wall 312 extends from the periphery ofbase 310 towards proximal end 308. Preferably, cylindrical wall 312extends axial with longitudinal axis A.

Cap 302 also includes a piston member 314. Piston member 314 isconfigured to seat valve prosthesis 200. Piston member 314 can includean elongate cylinder portion 316. Cylinder portion 316 extends from base310 towards proximal end 308. Piston member 314 can also include a discportion 318 at the proximal end of cylinder portion 316. Disc portion318 has an outer diameter that is larger than the outer diameter ofcylinder portion 316. In the illustrated embodiment, base 310,cylindrical portion 316, and disc portion 318 define an opening 328.Opening 328 can extend from distal end 306 of cap 300 to the proximalend of the disc portion 318 along longitudinal axis A.

Extending from the proximal end of the disc portion 318 is a cylindricalwall 320. Cylindrical wall 320 has a surface 322 at its proximal end.Piston member 314 can include at least one side wall 324. In theillustrated embodiment, piston member 314 includes three side walls 324.Side walls 324 extend from cylindrical wall 320 towards proximal end308. Side walls 324 are preferably equally and circumferentially spacedaround the periphery of cylindrical wall 320. As side walls 324 extendtowards proximal end 308, side walls 324 preferably move away fromlongitudinal axis A. Side walls 324 are generally triangular—the widthof side walls 324 at the proximal end is greater than the width of sidewalls 324 at the distal end. Each side wall 324 has an arcuate innersurface 326. Side walls 324 can be formed in other configurations. Forexample, side walls 324 can have a constant width, or side walls 324 canextend axially with longitudinal axis A. Piston member 314 can includeone side wall, two side walls, or more than three side walls. Forreasons discussed below, piston member 314 preferably includes aseparate side wall 324 for each support arm 214 of valve prosthesis 200,and each side wall 324 is preferably sized to cover a majority ofsupport arm 214.

Valve prosthesis 200 can be seated in the recess defined by the discportion 318 and cylindrical wall 320 at the distal end, and the sidewalls 324 circumferentially. Preferably, valve prosthesis 200 isorientated such that distal end 206 faces piston member 314. Distal end206 of valve prosthesis 200 is inserted against surface 322. An outerdimension of frame 202 of valve prosthesis 200 can be compressed orreduced prior to being seated in the piston member 314. For example, aportion of or the entire external dimension of prosthesis 200 may bereduced by hand, or otherwise, such that the outer dimension of theprosthesis 200 is at least slightly smaller than the recess defined bythe proximal end of side walls 224.

Side walls 324 contact side portions of valve prosthesis 200. In anembodiment, side walls 324 contact and enclose, at least a portion of,support arms 214 of valve prosthesis 200. In the illustrated embodimentof valve prosthesis 200, support arms 214 are biased away from supportframe 202. Preferably, as valve prosthesis 200 is inserted in the recessdefined by the disc portion 318 and cylindrical wall 320 at the distalend, and the side walls 324 circumferentially, side walls 324 contactsupport arms 214. Side walls 324 gradually pivot support arms 214radially inward towards support frame 202 as valve prosthesis 200 isinserted. Accordingly, side walls 324 guide and protect support arms 214of valve prosthesis 200 during loading by covering at least a portion ofsupport arms 214 and by reducing the external dimension of the supportarms 214. This protection reduces the risk that support arms 214 willprolapse during loading.

Preferably, base 310, cylindrical wall 312, and piston member 314 areconcentric with longitudinal axis A to define a chamber 330 betweencylindrical wall 312 and piston member 314.

Reducing member 304 has a distal end 332, a proximal end 334, and alongitudinal axis B. Reducing member 304 can include a cylindrical wall336. Cylindrical wall 336 has an inner surface 338 (shown in FIGS. 4Aand 4B) and an outer surface 340. Preferably, cylindrical wall 336 isaxial with longitudinal axis B.

Reducing member 304 can include a conical wall 342. In the illustratedembodiment, conical wall 342 is connected to the proximal end ofcylindrical wall 336. Conical wall 342 has an inner surface 344 (shownin FIGS. 4A and 4B) and an outer surface 346. The inner diameter ofconical wall 324 decreases toward proximal end 334. As best illustratedin FIG. 4A, inner surface 344 has a curved profile. Alternately, innersurface 344 can have a planar profile. Reducing member 304 can alsoinclude a plurality of tabs 354. Tabs 354 extend radially from conicalwall 342 to allow a user to securely grasp reducing member 304 and toprevent rotation thereof during loading.

Cylindrical wall 336 and conical wall 342 define a chamber 348 (shown inFIGS. 4A and 4B). Chamber 348 can have a first open end 350 defined bycylindrical wall 336 and a second open end 352 defined by conical wall342. First open end 350 is sized to accept piston member 314 of cap 302and a valve prosthesis 200 seated in piston member 314. Second open end352 is sized to allow at least a portion of proximal end 212 of valveprosthesis 200 to protrude through second open end 352 when valveprosthesis 200 is inserted in chamber 348.

The chamber 330 of cap 302 is sized to accept the cylindrical wall 336of reducing member 304 as the proximal end 308 of cap 302 is advancedwithin chamber 348. In this position, outer surface 340 of cylindricalwall 336 faces the inner surface of cylindrical wall 312. When thedistal end of cylindrical wall 336 of reducing member 304 contacts base310 of cap 302, advancement of piston member 314 within chamber 348 isstopped at a desired final position within chamber 348 of reducingmember 304. As piston member 314 advances within chamber 348, theportion of valve prosthesis 200 that is proximal to and unenclosed byside walls 324 contacts the inner surface 344 of conical wall 342,compressing or reducing the outer diameter of valve prosthesis 200.Preferably, in the final position, the coupling members 210 areprotruding from second open end 352 of reducing member 304.

In an embodiment, cap 302 can be selectively coupled with reducingmember 304. Any suitable means of connection between cap 302 andreducing member 304 may be used. In the embodiment illustrated in FIG.3, cylindrical wall 336 defines longitudinal notch 355, a firstcircumferential notch 357, and a second circumferential notch 358.Longitudinal notch 355, first circumferential notch 357, and secondcircumferential notch 358 are configured to receive two projections (notshown) formed on the inner surface of cylindrical wall 312. Cap 302 canbe coupled to reducing member 304 by rotating cap 302 relative toreducing member 304. Other suitable means of connection may includecorresponding threads or a frictional fit, for example.

FIGS. 5, 6A, and 6B illustrate an alternate embodiment of piston member314. Piston member 314 includes cylinder portion 316 that extends frombase 310. Cylindrical wall 320, however, extends directly from theperiphery of cylinder portion 316, defining a surface or lip 356. Sidewalls 324 extend from cylindrical wall 320 as described above. Thisembodiment omits disc portion 318. Valve prosthesis 200 can be seated inthe recess defined by lip 356, cylindrical wall 320, and side walls 324.Preferably, valve prosthesis 200 is orientated such that distal end 206faces piston member 314. Distal end 206 of valve prosthesis 200 isinserted against lip 356.

FIG. 7 illustrates an alternate embodiment of cap 302 having an optionalfriction interface surface. In the illustrated embodiment, piston member314 further includes an O-ring 360. O-ring 360 encircles side walls 324at the distal end, near cylindrical wall 320. At least a portion of theinner surface of O-ring 360 extends into the recess defined by thecylindrical wall 320 and the side walls 324. The portions of the innersurface of O-ring 360 that extend into the recess define the optionalfriction interface surface. When valve prosthesis 200 is inserted intothe recess, at least a portion of the outer surface of valve prosthesis200, for example, a portion of frame 202, contacts the inner surface ofO-ring 360 that extends into the recess. The contact between valveprosthesis 200 and O-ring 360 creates a friction interface that preventsvalve prosthesis 200 from moving, including translation and rotation,while the exposed portion of valve prosthesis 200 contacts inner surface344 of conical wall 342, compressing or reducing the outer diameter ofvalve prosthesis 200. O-ring 360 can be a polymeric material or anyother material with a coefficient of friction sufficient to preventvalve prosthesis 200 from moving and that is suitable for use insurgical procedures. Other suitable means for creating the frictioninterface surface can be used, including, for example, liningcylindrical wall 320 with a polymeric lining or inserting a polymericwasher in the recess defined by cylindrical wall 320.

FIGS. 8-16 illustrate methods of loading a valve prosthesis 200 onto adelivery system, for example, catheter assembly 100. In FIG. 8, distalend 104 of catheter assembly 100 is passed through reducing member 304such that valve retaining sleeve 114, valve retainer 116, and distal tipassembly 108 pass through second open end 352 and first open end 350.Preferably, this step is performed in a saline bath 400 such that distaltip assembly 108 never leaves the saline solution in saline bath 400.

In FIG. 9, valve prosthesis 200 is seated in piston member 314 of cap302. This step can be performed inside or outside of saline bath 400.Valve prosthesis 200 is aligned with longitudinal axis A of cap 302 andoriented so distal end 206 of valve prosthesis 200 is facing pistonmember 314. Valve prosthesis is inserted in the recess defined, in part,by side walls 324 until the distal end 206 contacts a surface of pistonmember 314, for example, surface 322 or lip 356. A user can compress orreduce the outer dimension of frame 202 of valve prosthesis 200 prior toseating it in piston member 314. Support arms 214 are centered behindside walls 324 such that, at least, the apexes of support arms 214 iscovered by side walls 324. Preferably, as valve prosthesis 200 isinserted in the recess, side walls 324 contact and radially pivotsupport arms 214 inward towards the center of valve prosthesis 200.

In FIG. 10, cap 302 having valve prosthesis 200 seated in piston member314 is placed over distal tip assembly 108. Distal tip assembly 108 isaligned with an opening defined by valve leaflets 204 of valveprosthesis 200 and opening 328 of cap 302, and advanced therein. In anembodiment, distal tip assembly 108 is advanced until at least a portionof distal tip assembly 108 protrudes through opening 328 at distal end306 of cap 302. Preferably, this step is performed in saline bath 400.

In FIG. 11, reducing member 304 is advanced toward cap 302 having valveprosthesis 200 seated therein. Reducing member 304 is advanced overpiston member 314, causing the proximal end 212 of valve prosthesis 200to slide along inner surface 344 of conical wall 342. As valveprosthesis 200 slides along inner surface 344 towards second open end352, the external dimension of the valve prosthesis 200 is reduced.Preferably, during this step, no air is present in loading device 300 toreduce the risk that flushing is impacted. Preferably, as shown in FIG.12, proximal end 334 of reducing member 304 is radially aligned withcatheter assembly 100 such that second open end 352 is aligned with thedistal end of valve retainer 116. When cap 302 places valve prosthesis200 in the final desired position, cap 302 is selectively coupled withreducing member 304. At this point, preferably, a portion of proximalend 216 of valve prosthesis 200 protrudes from second open end 352,including coupling members 210, for example.

In FIG. 13, valve prosthesis 200 is coupled to valve retainer 116.Coupling members 210, protruding from second open end 352, are insertedin slots 120 of valve retainer 116, preventing valve prosthesis 200 frommoving apart from catheter assembly 100. Loading device 300 or catheterassembly 100 can be rotated to correctly align coupling members 210 withslots 120 for insertion.

In FIG. 14, valve retaining sleeve 114 is advance over the proximal end216 of valve prosthesis 200 that has a reduced external dimension. Toadvance valve retaining sleeve 114 over valve prosthesis 200, outerdelivery shaft 110 and coupled valve retaining sleeve 114 can beextended over valve prosthesis 200, or alternately, intermediatedelivery shaft 118 and coupled valve retainer 116 can be retractedwithin valve retaining sleeve 114. In an embodiment, valve retainingsleeve 114 is advanced over crimped portion of valve prosthesis 200until the proximal end of valve retaining sleeve 114 is adjacent theproximal end of valve retainer 116. At this point, as illustrated inFIG. 15, valve retaining sleeve 114 encompasses the portion of frame 202attached to the valve skirt 208, not encompassing support arms 214.

In FIG. 16, cap 302 and reducing member 304 are uncoupled. Cap 302 isdisengaged from valve prosthesis 200 and removed by advancing overdistal tip assembly 108. At this point, valve prosthesis 200 is loadedon catheter assembly 100.

While various embodiments of the present invention have been describedabove, they have been presented by way of example only, and notlimitation. The elements of the embodiments presented above are notnecessarily mutually exclusive, but can be interchanged to meet variousneeds as would be appreciated by one of skill in the art.

It therefore will be apparent to one skilled in the art that variouschanges in form and detail can be made to the embodiments disclosedherein without departing from the spirit and scope of the presentinvention. The phraseology or terminology herein is used for descriptionand not for limitation. Thus, it is intended that the present inventioncover modifications and variations of this invention provided they comewithin the scope of the appended claims and their equivalents.

1. A device for loading a prosthesis onto a delivery system, theapparatus comprising: a cap having a proximal end, a distal end, and apiston member, the piston member includes a first surface configured tocontact a first end of the prosthesis seated therein, the piston memberincludes at least one side wall extending from a periphery of the firstsurface, the at least one side wall is configured to contact a portionof the side of the prosthesis seated therein; and a reducing memberhaving a conical wall, a first open end, and a second open end, thefirst open end is configured to receive the piston member, wherein thereducing member reduces an external dimension of at least a portion ofthe prosthesis seated in the piston member as the prosthesis is movedalong an inner surface of the conical wall.
 2. The loading device ofclaim 1, wherein the reducing member further comprises a cylindricalwall that defines the first open end, and wherein the conical surfacedefines the second open end.
 3. The loading device of claim 1, whereinthe cap is configured to releasably couple with the reducing member. 4.The loading device of claim 1, wherein the at least one side wall of thepiston member comprises at least two side walls that are spaced aroundthe periphery of the first surface.
 5. The loading device of claim 1,wherein the prosthesis is a valve prosthesis having at least one supportarm, and the portion of the side of the valve prosthesis that the atleast one side wall contacts is a portion of the at least one supportarm.
 6. The loading device of claim 1, wherein the at least one sidewall has a first width at a distal end of the at least one side wall,the at least one side wall has a second width at a proximal end of theat least one side wall, and the second width is greater than the firstwidth.
 7. The loading device of claim 1, wherein the second open end ofthe reducing member is sized to allow at least a portion of a second endof the prosthesis to pass through.
 8. A method for loading a prosthesisonto a delivery system, the method comprising: passing a distal end of adelivery system through a first open end and a second open end of areducing member, seating the prosthesis in a piston member of a cap bycontacting a first end of the prosthesis with a first surface of thepiston member and by contacting a portion of a side of the prosthesiswith at least one side wall extending from the periphery of the firstsurface; inserting the distal end of the delivery system into a centerof the prosthesis and an opening defined by the piston member; andadvancing the cap towards a reducing member such that a portion of theprosthesis seated in the piston member advances along an inner surfaceof the conical wall of the reducing member.
 9. The method of claim 8,further comprising coupling the cap with the reducing member.
 10. Themethod of claim 8, further comprising: coupling a second end of theprosthesis to a prosthesis retainer of the delivery system; andadvancing a retaining sleeve over at least a portion of the prosthesisthat has been advanced along the conical wall of the reducing member.11. The method of claim 10, further comprising advancing the pistonmember and the reducing member away from the prosthesis retained withinthe retainer sleeve.
 12. The method of claim 10, wherein advancing thecap towards a reducing member further comprises advancing at least aportion of the second end of the prosthesis through a first open end ofthe reducing member.
 13. The method of claim 12, wherein the at least aportion of the second end of the prosthesis comprises at least onecoupling member, and wherein coupling the second end of the prosthesisto the prosthesis retainer comprises engaging each of the at least onecoupling member with a slot in the prosthesis retainer.
 14. The methodof claim 8, wherein the prosthesis is a valve prosthesis having at leastone support arm, and wherein seating the valve prosthesis in the pistonmember comprises inserting the valve prosthesis in a recess defined atleast in part by the first surface and the at least one side wall, andcentering the at least one support arm of the valve prosthesis with theat least one side wall of the piston member.
 15. The method of claim 14,wherein the at least one side wall of the piston member comprises atleast two walls, and wherein the at least one support arm comprises atleast two support arms.